C++ 重载操作符

class Even{
    int number=0;
    public:
    A & operator ++ (){
        number +=2;
        return *this;
    }
    A operator ++ ( int ){
        int old = number;
        ++(number);
        return old;
    }
}

class Matrix{
    int ** elements;
    int sizeX;
    int sizeY;
    public:
    Matrix & operator + ( const Matrix & m ) const{
        int newX = m.getX() > this.sizeX ? m.getX() : this.sizeX;
        int newY = m.getY() > this.sizeY ? m.getY() : this.sizeY;
        Matrix _new(newX,newY);
        for( int i = 0; i< newX; i++ ){
            for( int j =0; j< newY; j++ ){
                _new[i][j] = m[i][j] + elements[i][j];
            }
        }
        return _new;
    }
}